If you understand what is electrical resistance you will get the answer to your question. Resistance, measured in units of OHMS (Ω) is an electrical quantity that measures how a device controls the electric current flow through it.
Resistance calculation with Ohm’s law:
R = V ÷ I
R is the resistance
V is the voltage
I is the current
We have two bulbs, 100 W, and 60 W – I assume the voltage is 234 V 50 Hz single phase A.C. the standard supply in the country.
Next, let’s find out the current drawn by the two bulbs:
100 W ÷ 234 V = 0.43 Amps
60 W ÷ 234 V = 0.25 Amps
Now, find the resistance using Ohms law.
You will find the answer.